Over the past 15 years, investigators at Triangle Research and Development Corporation (TRDC) have developed a series of significantly improved two-component coolants for aircraft avionics, spacecraft and metalworking operations using phase change materials or microPCMs. These fluid slurries utilize the high latent thermal capacitance of microencapsulated paraffins to significantly enhance the thermal storage and transport properties of commercially available fluid coolants. During SBIR programs for NASA, USAF, NAVY, SDIO and NSF, the new coolants have been demonstrated to enhance fluid thermal capacitance up to 40x or 4,000 percent above the property of the base fluid. At the same time, the heat transport coefficient was observed to increase up to 3x or 300 percent. In Phase I and II SBIR programs for machining with NSF in 1990-94, investigators found that the microPCM coolants reduced tool wear over 25 percent and surface temperatures by 15 percent. They also observed there was over 90 percent reduction in smoke or evaporated coolants because of their much higher heat capacity, but this phenomenon was not investigated further at that time. The goal of this proposed effort is to investigate this potentially advantageous property. MicroPCM metalworking coolants will be prepared and used in metalworking experiments in the School of Public Health at UNC-Chapel Hill. Particulate sizes, level and the quantity of evaporated microPCM coolants will then be compared to that of a control coolant without particles in high speed turning experiments. Although microPCM particles are now used in apparel, the potential toxicity of the new coolants at high temperatures will also be investigated. PROPOSED COMMERCIAL APPLICATION: General Motors became our Phase III commercial partner following the NSF SBIR machining program and showed that microPCM coolants were useful for grinding and turning operations. Development of superior and safer metalworking coolants could significantly improve air quality about machining operations and reduce the evaporated loss of metalworking coolants. MicroPCM costs are rapidly dropping because of the increased use of microPCMs in footwear and clothing.